Hello HomerJ,
The recommended would be to reimport the user from the source if using LDAP/AD to feed your user information. You could also use the OTA or REST implementation to update the information as well, however that really only works for changing individual user information and not bulk user data. Each user can change and update limited information from within their customization settings upon logging into ALM (this could save the admins some time).

However the best way to edit some of the information such as email domain name changes, office location changes and various other changes that would need to be updated in large bulk could be facilitated through the manipulation of the back end USER table within the qcsiteadmin_db

***note changing this should be done with care and only by trained DBAs with knowledge of back end queries and all changes should be done with the knowledge of risk that things could be corrupted, and all changes should have been backed up prior to any changes being instituted in case things should need to be reversed.

Her is an example of a basic query that could be used to change the email domain name for a corporation (the same changes could be instituted for various other things such as office location, etc through the tweaking of the fields that would need updating. Your DBA probably has a better query algorithm but this is just an example of something that could be attempted:

UPDATE td.USERS SET EMAIL =
(SELECT SUBSTRING(EMAIL, 0, PATINDEX('%@%',EMAIL)) + '@domiain.com'
from td.USERS U WHERE U.USER_ID = USERS.USER_ID)
where EMAIL is NOT NULL;

This is not necessarily complete and full and only offered for an educational example and to be tested and adjusted accordingly prior to actually usage and even then at the users own risk.

Once these changes are made they will dynamically be propagated to the ALM server without intervention necessary which is why caution must be exercised when making such changes.

Hope this helps,
Dan